This invention relates generally to sawmill equipment and more particularly to an apparatus and method for cutting a log into suitable lengths.
One of the first steps in converting a tree into lumber is to first cut the tree into suitable log lengths. It is important that the tree be bucked or cut into lengths that will produce the highest possible value of lumber for that tree. During the bucking procedure it is also desirable that defective or excessively crooked wood be cut out of the tree. Such wood is subsequently sent to a chipper for conversion into chips and later pulped. Cutting decisions made during bucking have traditionally been exercised by a highly skilled operator, but computer systems have been recently developed which scan the log and advise the operator as to the most appropriate lengths.
Two types of bucksaw systems are typically utilized. The simplest system is known as the cutoff saw system. In this system the log travels endwise down a conveyer and the operator activates a so-called length stop when he has decided where a cut should be made. The forward end of the log hits the stop, the conveyer is shut down, and the saw is activated to make the desired cut. The log stop is then retracted, and conveyer travel is resumed. Once the cut log has passed the stop, the stop is re-extended, causing the leading end of the remaining part of the tree to run into the stop, and the process is repeated.
The cutoff saw system gives the operator a great amount of versatility because he can cut the log at any point by merely stopping the log on the conveyer, and can reject wood to the chipper by cutting out undesirable sections. However, due to the intermittent nature of the cutoff saw system, it is very slow, resulting in poor productivity. Bucksaw productivity is extremely important because a bottleneck will usually exist in the sawmill at the bucksaw.
A second type of bucksaw which is more commonly used is the slasher deck system. This system is more elaborate than the cutoff saw system and has far greater capabilities. In this system trees are conveyed laterally on lug transfer chains which pass under a series of saws spaced at predetermined increments. Using special log loaders, the operator loads individual trees onto each log space of a continuously moving transfer deck. As each tree is moving toward the saws, the operator is positioning the saws as desired to make the necessary cuts. When the tree reaches the saws, the saws are displaced into the tree to make all of the required cuts at once.
A slasher deck system is far more productive than a cutoff saw system. However, there are a number of drawbacks with a slasher deck system. The system is very elaborate and is therefore expensive to purchase and maintain. Moreover, despite the complex construction of this type of system, it is very difficult to precisely space the saws so that the cut is made exactly where desired. Often the saws are merely placed at commonly required cut points rather than being specifically positioned for each particular log. This results in crooks and other defects remaining in the logs, which produces lower quality lumber and might even require that a cut log be subsequently passed to a chipper as a result of the failure to identify and remove a defect at an early point in the sawmill cycle.
A slasher deck system also takes up a great deal of space. The sheer size of the system also sometimes permits logs to become crossed as they move across the deck on the chains. To correct such faulty positioning, the operator must pry the logs back into a correct position. This can at times be a very dangerous procedure both to the equipment and to personnel.
It is therefore an object of the present invention to provide a bucksaw apparatus and method which overcomes the drawbacks and limitations of the prior proposals. More specifically, the invention has as its objects the following:
(1) to provide a bucking system which gives the operator as much control as possible to cut logs of different lengths while removing defects and damaged portions; PA1 (2) to develop a bucking system which is physically small, simple in construction, and low in initial and operating costs; PA1 (3) the provision of a bucksaw system which may be continuously operated to reduce or eliminate the bottleneck present in existing systems at this point in the system; and PA1 (4) the development of a bucksaw which can be substituted for existing cutoff and slasher deck systems without disrupting or requiring replacement of the remaining portions of the production line.